The present invention relates to a high voltage apparatus with a three-dimensional structure, comprising a plurality of electric units, and a frame having a plurality of insulating columns, the electric units being mounted in a plurality of stages between adjacent insulating columns.
High voltage apparatuses of the type described above are widely adapted for equipment to be used in electric power systems. A typical example of such a high voltage apparatus is a thyristor converter for use in high voltage direct current transmission or for use in an interlink of electric power systems of different frequencies. In a thyristor converter of this type, a number of thyristor modules are mounted in multistages between a plurality of insulating columns of a storage frame. In such a thyristor converter, the insulating columns must be able to provide excellent insulation between the electric units at different potentials and must also have sufficient mechanical strength to withstand the weight of the electric units as well as the earthquake. With recent increases in the demand for electric power, electric power systems of higher voltage and current are required and, hence, electric equipment of greater size is required. With such a trend, increases in the installation area of the equipment present a problem.
In order to solve this problem, electric equipment with tall insulating columns are required. The insulating columns used in the electric equipment must also have better insulating performance and higher mechanical strength, resulting in higher cost.
In order to clarify the problems encountered with insulating columns used in a conventional high voltage apparatus, a high voltage apparatus with conventional insulating columns will first be described with reference to FIGS. 1, 2 and 3. An example of a high voltage apparatus shown in these figures is a thyristor converter which uses, in this example, thyrisor modules as electric units or modules 14.
FIG. 1 shows a high voltage apparatus 10 with conventional insulating columns. The high voltage apparatus 10 has a storage frame 12, and a number of electric units or modules 14 of substantially identical shape mounted on the frame 12. The storage frame 12 has substantially horizontal upper and lower frames 16 and 18 with a distance therebetween, a base frame 20 placed on the floor, support insulators 22 interposed between the lower frame 18 and the base frame 20, and three insulating column 24 of an electrical insulating material which are mounted in a substantially vertical position between the upper and lower frames 16 and 18. Each insulating column 24 comprises a columnar body 26 extending between the upper and lower frames 16 and 18, and a plurality of module supports 28 which adhere to the columnar body 26 at predetermined intervals and which project therefrom. Each module 14 has a metallic casing 30, and a pair of mounting arms 32 and 34 projecting from both sides of the casing 30. Each module 14 is horizontally arranged between two adjacent insulating columns 24. The mounting arms 32 and 34 are mounted to the module supports 28 at the right and left of FIG. 1 with nuts and bolts.
In this manner, in the high voltage apparatus 10 shown in FIG. 1, the modules 14 are vertically arranged in a plurality of stages (only three are shown in the figure for the sake of simplicity), and are horizontally arranged in two rows. If the capacity of the apparatus 10 is increased, the number of stages of the vertically arranged modules 14 may be increased, and/or number of rows of the horizontally arranged modules 14 may be increased. In the latter case, the number of insulating columns 24 and the number of modules 14 which may be horizontally arranged may be increased.
FIGS. 2 and 3 show a state wherein the mounting arm 34 of a module 14a and the mounting arm 32 of a module 14b are mounted on the module supports 28 mounted on the central insulating column 24 in FIG. 1. Symbols a, b, and so on are added to reference numeral 14 for the purpose of differentiating different modules 14; reference numeral 14 will be used to generally refer to the modules. As shown in FIGS. 2 and 3, the module support 28 is a square plate with a central hole. The mounting arms 32 and 34 are of a rectangular shape and are fixed to the module supports 28 at the two sides of the columnar body 26 by means of nuts 38 and bolts 36.
Although the conventional high voltage apparatus 10 as described above is widely adopted, there is still room for improvement. First, two vertically arranged modules 14b and 14c shown in FIG. 1 must have a relatively large distance therebetween. Insulation between the modules 14b and 14c at different potentials is achieved through portions 35 of columnar bodies 26b and 26c between the module supports 28. Unlike general insulators, the columnar bodies 26 can not have ribs therearound for increasing the creeping distance. Thus, the length of the portion 35 must be prolonged, requiring a long distance for insulating between the vertically arranged modules 14b and 14c. This requirement makes the design of the apparatus difficult when it is desired to lessen the height of the high voltage apparatus or when it is desired to stack more stages of modules than is conventionally possible.
Secondly, elongate materials having high mechanical strength and insulating performance must be used in order to securely support several modules 14 by insulating columns 24, which are prepared by adhering a plurality of module supports 28 to elongate columnar bodies 26, while providing sufficient insulation between the horizontally arranged modules at different potentials. Such materials are hard to obtain, resulting in increased cost of the apparatus. This has become a big problem in the manufacture of high voltage apparatuses of large capacity and of multistage type.
Even if expensive materials as described above are used, the overall insulating column 24 is subject to the problem of poor reliability of mechanical strength since the columnar body 26 and the module support 28 are joined, for the sake of insulation, with an adhesive. An adhesive is conventionally used to join the columnar body 26 to the module support 28 since metallic bolts or the like lead to a difficult problem of insulation between the modules 14a and 14b supported by the module supports 28.
In summary, a high voltage apparatus with conventional insulating columns has a large height, low resistance to earthquakes (due to its large height) and lower insulating performance of the insulating columns. Therefore, a high voltage apparatus is desired which is not subject to the problems encountered with conventional insulating columns and which uses insulating columns made of an inexpensive material.